U.S. patent application number 11/225101 was filed with the patent office on 2006-04-13 for detection device for decreased tire pressures and method thereof.
This patent application is currently assigned to Sumitomo Rubber Industries, Ltd.. Invention is credited to Yuji Oshiro.
Application Number | 20060076095 11/225101 |
Document ID | / |
Family ID | 35511267 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060076095 |
Kind Code |
A1 |
Oshiro; Yuji |
April 13, 2006 |
Detection device for decreased tire pressures and method
thereof
Abstract
To provide a device for detecting whether heterogeneous tires
are mounted on the respective left and right driving wheels or not
and accurately detecting the decreased tire pressures. The
detection device of heterogeneous tires of the present invention is
equipped with a means for detecting the rotational speeds of wheels
mounted on a vehicle, a means for detecting torque applied to
driving wheels, and a calculation means for calculating the
inclinations of regression straight lines of respective relations
from relation between the rotational speed ratio of the front and
rear wheels in the left side wheels of the vehicle and torque
applied to driving wheels and relation between the rotational speed
ratio of the front and rear wheels in the right side wheels of the
vehicle and the torque, and detects that heterogeneous tires are
mounted on the driving wheels by comparing the inclination of
regression straight line of the relation of the left side wheels
with the inclination of regression straight line of the relation of
the right side wheels. The detection device of the decreased tire
pressures of the present invention changes the threshold for
judging tire deflation to a threshold in a case of loading
heterogeneous tires when it detects that the heterogeneous tires
are mounted on the driving wheels.
Inventors: |
Oshiro; Yuji; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Sumitomo Rubber Industries,
Ltd.
|
Family ID: |
35511267 |
Appl. No.: |
11/225101 |
Filed: |
September 14, 2005 |
Current U.S.
Class: |
152/154.1 |
Current CPC
Class: |
B60C 23/003 20130101;
B60C 23/061 20130101 |
Class at
Publication: |
152/154.1 |
International
Class: |
F16F 15/32 20060101
F16F015/32 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2004 |
JP |
2004-277584 |
Claims
1. A detection device of heterogeneous tires for detecting whether
the kind of tires differs or not based on the rotational speeds of
wheels mounted on a vehicle, comprising a calculation means for
calculating the inclination of respective relational straight lines
from relation between a ratio of the rotational speed of a front
wheel to that of a rear wheel in the left side wheels of the
vehicle and torque applied to driving wheels and relation between a
ratio of the rotational speed of a front wheel to that of a rear
wheel in the right side wheels of the vehicle and the torque
applied to driving wheels, wherein heterogeneous tires being
mounted on the driving wheels are detected by comparing the
inclination of the relation of the left side wheels with the
inclination of the relation of the right side wheels.
2. A detection method of heterogeneous tires for detecting whether
the kind of tires differs or not based on the rotational speeds of
wheels mounted on a vehicle, comprising a step of calculating the
inclination of respective relational straight lines from relation
between a ratio of the rotational speed of a front wheel to that of
a rear wheel in the left side wheels of the vehicle and torque
applied to driving wheels and relation between a ratio of the
rotational speed of a front wheel to that of a rear wheel in the
right side wheels of the vehicle and the torque applied to driving
wheels, wherein heterogeneous tires being mounted on the driving
wheels are detected by comparing the inclination of the relation of
the left side wheels with the inclination of the relation of the
right side wheels.
3. A detection program of heterogeneous tires for functionalizing a
computer as a calculation means for calculating the inclination of
each of relational straight lines from relation between a ratio of
the rotational speed of a front wheel to that of a rear wheel in
the left side wheels of the vehicle and torque applied to driving
wheels and relation between a ratio of the rotational speed of a
front wheel to that of a rear wheel in the right side wheels of the
vehicle and the torque applied to driving wheels, and a means for
detecting that heterogeneous tires are mounted on the driving
wheels by comparing the inclination of the relation of the left
side wheels with the inclination of the relation of the right side
wheels, in order to detect whether the kind of tires differs or not
based on the rotational speeds of wheels mounted on a vehicle.
4. A detection device for the decreased tire pressures, wherein the
detection device of heterogeneous tires according to claim 1 is
employed.
5. A detection device of the decreased tire pressures for detecting
the decreased pressures of a tire mounted on a vehicle based on the
rotational speeds of wheels mounted on a vehicle, comprising a
means for detecting the rotational speeds of wheels, a means for
detecting torque applied to driving wheels, a calculation means for
calculating the primary coefficients of straight lines which
approximate primarily respective relations from relation between a
ratio of the rotational speed of a front wheel to that of a rear
wheel in the left side wheels of the vehicle and torque applied to
driving wheels and relation between a ratio of the rotational speed
of a front wheel to that of a rear wheel in the right side wheels
of the vehicle and the torque applied to driving wheels and a
detection means for heterogeneous tires which judges that
heterogeneous tires are respectively mounted on the left and right
driving wheels by comparing the primary coefficient of the relation
of the left side wheels with the primary coefficient of the
relation of the right side wheels; wherein a threshold for judging
the decreased tire pressures is changed to a threshold for a case
of loading heterogeneous tires when it is judged that the
heterogeneous tires are respectively mounted on the left and right
driving wheels.
6. A detection method of the decreased tire pressures, wherein the
detection method of heterogeneous tires according to claim 2 is
included.
7. A detection method of the decreased tire pressures for detecting
the decreased tire pressures mounted on a vehicle based on the
rotational speeds of wheels mounted on a vehicle, comprising the
steps of detecting the rotational speeds of wheels, detecting
torque applied to driving wheels, calculating the primary
coefficients of straight lines which approximate primarily
respective relations from relation between a ratio of the
rotational speed of a front wheel to that of a rear wheel in the
left side wheels of the vehicle and torque applied to driving
wheels and relation between a ratio of the rotational speed of a
front wheel to that of a rear wheel in the right side wheels of the
vehicle and the torque applied to driving wheels and judging that
heterogeneous tires are respectively mounted on the left and right
driving wheels by comparing the primary coefficient of the relation
of the left side wheels with the primary coefficient of the
relation of the right side wheels; wherein a threshold for judging
the decreased tire pressures is changed to a threshold for a case
of loading heterogeneous tires when it is judged that the
heterogeneous tires are respectively mounted on the left and right
driving wheels.
Description
BACKGROND OF THE INVENTION
[0001] The present invention relates to a device for detecting
decreased pressures of tires mounted on a vehicle and a method
thereof. More specifically, the present invention relates to a
device and a method for accurately detecting the decreased tire
pressures by detecting that the kind of tires mounted on a vehicle
differs.
[0002] When the pressures of tires mounted on a vehicle are
decreased, a fuel mileage is deteriorated and there is danger of
provoking burst at high speed running. When the tire pressures are
reduced, decreased pressure is detected, utilizing the change of
properties of tires such as the decrease of the dynamic load radii
of tires and the change of resonance frequency.
[0003] For example, a conventional detection device for the
decreased tire pressures uses a principle that since the outer
diameter of a tire (the dynamic load radius of a tire) is reduced
more than that of a tire having normal inner pressure when the
pressure of a specified tire of a vehicle is reduced, rotational
angular velocity is increased as compared with other normal tires.
For example, a method for detecting the decrease of inner pressure
from the relative difference of the rotational angular velocities
of tires uses the value obtained from following formula as a
judging value;
DEL={(F1+F4)/2-(F2+F3)/2}/{(F1+F2+F3+F4)/4}.times.100 (%) (Japanese
Unexamined Patent Publication No. 305011/1988). Wherein F1 to F4
are the rotational angular velocities of a front left tire, a front
right tire, a rear left tire and a rear right tire,
respectively.
[0004] However, when the kind of tires mounted differs, the
decreased tire pressures cannot be accurately detected.
[0005] Accordingly, a method for distinguishing the abrasion of a
tire and the kind of tires has been proposed.
[0006] The invention described in Japanese Unexamined Patent
Publication No. 188114/1997 discloses a method for distinguishing
the kind of tires mounted on a vehicle, for example, whether the
tire is a tire for summer or a tire for winter, by comparing the
inclination of a straight line which is obtained by plotting a
ratio of the rotational speed of a front wheel to that of a rear
wheel against the speed of a vehicle, with the data of a tire whose
kind is known by preliminary measurement.
[0007] The invention described in Japanese Unexamined Patent
Publication No. 78442/1999 uses relation between a ratio of the
rotational speed of a front wheel to that of a rear wheel and the
acceleration of a vehicle in order to detect the abrasion state of
tire.
[0008] The invention described in Japanese Unexamined Patent
Publication No. 79812/2000 discloses a method for distinguishing
whether the tire mounted on a driving axle is a tire for summer or
a tire for winter by utilizing the reciprocal number of a turning
radius using the judging value of tire deflation (DEL), but the
method is limited to a vehicle mounted with LSD (Limited Slip
Differential).
[0009] The invention described in Japanese Unexamined Patent
Publication No. 19435/2002 and Japanese Unexamined Patent
Publication No. 181669/2002 uses relation between a slip ratio (a
value obtained by dividing the difference between the rotational
speed of following wheels and the rotational speed of driving
wheels by the rotational speed of driving wheels) and the
acceleration of a vehicle, in order to distinguish the kind of
tires.
[0010] Japanese Unexamined Patent Publication No. 211220/2002
discloses a method for distinguishing the kind of tires in
accordance with the size of unevenness of the judging value of tire
deflation (the average of the absolute value of the judging value
of tire deflation).
[0011] The ratios of the rotational speeds of the front and rear
wheels of respective left and right wheels are not proportional to
the speed of a vehicle. For example, the ratio of the rotational
speeds of the front and rear wheels is larger at a rising gradient
road surface than that at a flat road even if its speed is slow.
Further, acceleration is small at the rising gradient road surface
but driving force is large; therefore the ratio of the rotational
speeds of the front and rear wheels is larger than that at a flat
road and the ratio of the rotational speeds of the front and rear
wheels is not proportional to the speed of a vehicle. Consequently,
it cannot be distinguished that the kind of left and right tires is
different even though relation between the ratios of the rotational
speeds of the front and rear wheels of respective left and right
wheels and the speed or acceleration of a vehicle is examined.
[0012] When the kind of tires differs depending on positions of a
vehicle, in particular, the kinds of tires respectively mounted on
the left and right driving wheels differ, the tire deflation cannot
be accurately judged by the threshold for judging tire deflation in
the case of loading the same kind of tires. Further, when the kinds
of tires respectively mounted on the left and right driving wheels
differ, driving properties differ at left and right; therefore
there are problems such as the distance of breakage becomes longer,
because slip is generated and braking operation does not work well.
Consequently, it is required that it is alarmed to a driver that
the kinds of tires respectively mounted on the left and right
driving wheels differ, and the vehicle control system (such as ABS
and TRC) is actuated in accordance with the different kind of
tires.
SUMMATY OF THE INVENTION
[0013] Although the abrasion tires and whether tires mounted at
time are tires for summer or tires for winter can be distinguished,
it has not conventionally been able to distinguish that the kind of
tires differs when the different kinds of tires are respectively
mounted on the left and right driving wheels.
[0014] It is the purpose of the present invention to provide a
device for accurately detecting whether the different kinds of
tires are respectively mounted on the left and right driving
wheels, without being limited to such as the situation of a road
surface and the composition of a vehicle in which LSD is
mounted.
[0015] Further, it is the purpose of the present invention to
provide a device for accurately detecting the decreased tire
pressures even if the different kinds of tires are respectively
mounted on the left and right driving wheels.
[0016] The detection device of heterogeneous tires of the present
invention is a device for detecting whether the kind of tires
differs or not based on the rotational speeds of wheels mounted on
a vehicle, and is characterized in that the device is equipped with
a calculation means for calculating the inclination of each of
relational straight lines from relation between a ratio of the
rotational speed of a front wheel to that of a rear wheel in the
left side wheels of the vehicle and torque applied to driving
wheels and relation between a ratio of the rotational speed of a
front wheel to that of a rear wheel in the right side wheels of the
vehicle and the torque applied to driving wheels, and detects that
heterogeneous tires are mounted on the driving wheels by comparing
the inclination of the relation of the left side wheels with the
inclination of the relation of the right side wheels.
[0017] In the present invention, the rotational speed of a wheel is
a product of the rotational angular velocity of a wheel with the
radius of a given tire.
[0018] In the present invention, for example, the following is
carried out in order to detect that the different kinds of tires
are mounted on the respective left and right driving wheels.
[0019] When the following formulae are represented from the
relation between a ratio of the rotational speed of a front wheel
to that of a rear wheel in the right side wheels of the vehicle and
the torque applied to driving wheels; Rotational speed of left
front wheel/rotational speed of left rear wheel Rotational .times.
.times. speed .times. .times. of .times. .times. left .times.
.times. front .times. .times. wheel / rotational .times. .times.
speed .times. .times. of .times. .times. left .times. .times. rear
.times. .times. wheel = a .times. .times. 1 .times. torque .times.
.times. to .times. .times. driving .times. .times. wheel + b
.times. 1 ##EQU1## Rotational .times. .times. speed .times. .times.
of .times. .times. right .times. .times. front .times. .times.
wheel / rotational .times. .times. speed .times. .times. of .times.
.times. right .times. .times. rear .times. .times. wheel = a
.times. .times. 2 .times. torque .times. .times. to .times. .times.
driving .times. .times. wheel + b .times. .times. 2 , .times.
##EQU1.2## [0020] it is judged that heterogeneous tires are mounted
on the driving wheels, when either of the relational formulae is
satisfied for a predetermined C or k. [0021] i) |a1-a2|>c [0022]
ii) a1/a2>k or [0023] iii) a2/a1>k
[0024] Further, the fore-mentioned predetermined C or k is set as;
c=|a1-a2|/M k=1+(a1/a2-1)/N (provided that a1>a2) [0025] from
|a1-a2| and a1/a2 (a1>a2) or a2/a1 (a2>a1), after the
fore-mentioned relations; Rotational .times. .times. speed .times.
.times. of .times. .times. left .times. .times. front .times.
.times. wheel / rotational .times. .times. speed .times. .times. of
.times. .times. left .times. .times. rear .times. .times. wheel = a
.times. .times. 1 .times. torque .times. .times. to .times. .times.
driving .times. .times. wheel + b .times. 1 ##EQU2## Rotational
.times. .times. speed .times. .times. of .times. .times. right
.times. .times. front .times. .times. wheel / rotational .times.
.times. speed .times. .times. of .times. .times. right .times.
.times. rear .times. .times. wheel = a .times. .times. 2 .times.
torque .times. .times. to .times. .times. driving .times. .times.
wheel + b .times. .times. 2 , .times. ##EQU2.2## [0026] are
determined by changing the kind of tires (for example, tires for
summer or tires for winter) by every vehicle brand.
[0027] For example, the denominator M or N of the fore-mentioned
formulae for determining c or k is 2, but the values of M and N can
be selected by vehicle brands and the kind of tires (for example,
tires for summer or tires for winter).
[0028] Further, the detection device of the decreased tire
pressures of the present invention is a device for detecting the
decreased tire pressures mounted on a vehicle based on the
rotational speeds of wheels mounted on a vehicle and is
characterized in that the device is equipped with a means for
detecting the rotational speeds of wheels, a means for detecting
torque applied to driving wheels, a calculation means for
calculating the primary coefficients of straight lines which
approximate primarily respective relations from relation between a
ratio of the rotational speed of a front wheel to that of a rear
wheel in the left side wheels of the vehicle and torque applied to
driving wheels and relation between a ratio of the rotational speed
of a front wheel to that of a rear wheel in the right side wheels
of the vehicle and the torque applied to driving wheels, and a
detection means for heterogeneous tires which judges that
heterogeneous tires are respectively mounted on the left and right
driving wheels by comparing the primary coefficient of the relation
of the left side wheels with the primary coefficient of the
relation of the right side wheels, and a threshold for judging the
decreased tire pressures is changed to a threshold in a case of
loading heterogeneous tires when it is judged that the
heterogeneous tires are respectively mounted on the left and right
driving wheels.
[0029] A conventional art has judged whether all tires are worn or
not and whether tires mounted are tires for summer or tires for
winter, but the present invention judges whether tires respectively
mounted on the left and right driving wheels are different kinds or
not.
[0030] According to the detection device of heterogeneous tires of
the present invention, it can be alarmed to a driver that
heterogeneous tires are mounted on the respective left and right
driving wheels and persuade the driver to exchange tires. Further,
according to the detection device of the decreased tire pressures
of the present invention, even if heterogeneous tires are mounted
on the respective left and right driving wheels, the tire deflation
can be accurately detected by setting to the judgment threshold of
the tire deflation in the case of loading heterogeneous tires.
Thereby, even if heterogeneous tires are mounted on the respective
left and right driving wheels, it can be accurately alarmed to a
driver that the tire deflation occurs. Referring to Example
described later, when the difference between drive torque--the
inclination of the rotational speed ratio property of front and
rear wheels at a right side and drive torque--the inclination of
the rotational speed ratio property of front and rear wheels at a
left side exceeds 0.2.times.10.sup.-5 in a FR vehicle
(Mercedes-Benz, E-class), it can be judged that heterogeneous tires
are mounted on the respective left and right driving wheels.
Further, in the same Example, a deflation rate at which the
decreased tire pressures is judged is 30%, the judgment threshold
of deflation in case that the same tires are mounted on the
respective left and right driving wheels is set as 0.1 and the
judgment threshold of deflation in case that heterogeneous tires
are mounted on the respective left and right driving wheels is set
as 0.13. Thereby, in a state in which one wheel is deflated by 10%,
deflation is not judged for either of a case that the same tires
are mounted on the respective left and right driving wheels and a
case that heterogeneous tires are mounted on the respective left
and right driving wheels, in a FR vehicle (Mercedes-Benz, E-class).
In a state in which one wheel is deflated by 30%, deflation can be
judged for either of a case that the same tires are mounted on the
respective left and right driving wheels and a case that
heterogeneous tires are mounted on the respective left and right
driving wheels.
[0031] According to the present invention, it can be accurately
judged that heterogeneous tires are mounted, therefore when
heterogeneous tires are mounted, optimum control in accordance with
different kinds of tires on the respective left and right driving
wheels can be carried out using the information for such as an ABS
(antilock brake system) system, a TRC (traction control system)
system.
[0032] For example, in the ABS system, it is inputted from the
detection device of heterogeneous tires of the present invention
that the kinds of tires on the respective left and right driving
wheels are different, and the distribution of the brake operating
power of respective wheels can be set in accordance with the kinds
of tires. In the ABS system, slipping (tire locking) is momentarily
detected and brake operating power is adjusted in real time, but
the maximum brake power just before respective wheels are locked
can be obtained by setting the brake operating power for every
wheel in accordance with the kinds of tires; therefore safer and
more reliable breakage can be realized. As a result, even though
the kinds of tires on the respective left and right driving wheels
are different, a car body is not inclined toward heading direction
under breakage and a driver can operate a brake in state in which
direction control is possible.
[0033] In the TRC system, it is inputted from the detection device
of heterogeneous tires of the present invention that the kinds of
tires on the respective left and right driving wheels are
different, and the more effective drive control of a vehicle can be
realized, for example, by adjusting the drive power distribution of
left and right wheels and setting the upper limit of drive power in
accordance with the kinds of tires to suppressing slip at start and
acceleration.
[0034] According to the detection device of heterogeneous tires of
the present invention, it can be accurately detected that
heterogeneous tires are mounted on the respective left and right
driving wheels irrespective of the state of a road surface and
without loading LSD on a vehicle.
[0035] Further, according to the detection device of the decreased
tire pressures of the present invention, even if heterogeneous
tires are mounted, the tire deflation can be accurately detected by
setting to the judgment threshold of deflation in the case of
loading heterogeneous tires.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a block diagram of one example of the detection
device of the decreased tire pressures related to the Embodiment of
the present invention;
[0037] FIG. 2 is a flow chart showing an example of the detection
method of heterogeneous tires related to the Embodiment of the
present invention;
[0038] FIG. 3 is a graph in which the rotational speeds of the
front wheels/the rotational speeds of the rear wheels at respective
left and right are plotted against driving torque in one example
when the same kind of tires at the respective left and right
driving wheels are mounted, related to the Embodiment of the
present invention; and
[0039] FIG. 4 is a graph in which the rotational speeds of the
front wheels/the rotational speeds of the rear wheels of respective
left and right sides are plotted against driving torque in one
example when heterogeneous tires at the respective left and right
driving wheels are mounted, related to the Embodiment of the
present invention.
DETAILED DESCRIPTION
[0040] The detection device of heterogeneous tires of the present
invention determines the inclinations of straight lines which were
obtained by primarily approximating relation between a ratio of the
rotational speed of a front wheel to that of a rear wheel and
torque to driving wheels, for respective left and right wheels,
compares the fore-mentioned inclinations of straight lines of the
left and right wheels, and judges that heterogeneous tires are
mounted on driving wheels when the difference of the inclinations
is a fixed threshold or more. Further, it can be judged which of
the left and right driving wheels slips easily, from the size of
the inclination. Further, the kinds of left and right tires can be
judged by comparing the fore-mentioned inclinations of straight
lines which were obtained by primary approximation during running,
with the relation (the inclinations of straight lines primarily
approximated) between the rotational speed ratio of the front and
rear wheels and torque to driving wheels which was preliminarily
measured by every kind of tires.
[0041] Since friction between road surface and tires-slip property
(.mu.-s property) differs, a slip rate (the rotational speed ratio
of the front and rear wheels) is changed. Since the slip rate is
proportional to driving force (torque) and following wheels do not
slip, the rotational speed of the following wheels/the rotational
speed of the driving wheels can be set as the slip rate (of
reciprocal value). Then, it can be accurately detected that
heterogeneous tires are mounted on the respective left and right
driving wheels, by comparing the driving force to the slip rate
property which was determined from the relation between the
rotational speed ratio of the respective front and rear wheels and
the driving force.
[0042] Further, when it is detected that heterogeneous tires are
mounted on the respective left and right driving wheels, it can be
prevented that the tire deflation is erroneously alarmed
nevertheless the tire pressures are not reduced, by changing the
threshold for judging deflation to a value corresponding to the
loading of heterogeneous tires.
[0043] The detection device of heterogeneous tires of the present
invention is not limited to a vehicle with 4 wheels when the
driving wheels are 2 wheels at left and right and the rotational
speed ratio of the following wheels/the rotational speed of the
left driving wheel and the rotational speed of the following
wheels/the rotational speed of the right driving wheel are set
against the following wheels at the same axle, and can be applied
also to a vehicle with 3 wheels and a vehicle with 6 wheels.
EMBODIMENT
[0044] FIG. 1 is a block diagram of the detection device of the
decreased tire pressures related to the Embodiment of the present
invention. The detection device 10 of the decreased tire pressures
inputs the driving torque of a vehicle from the torque sensor 1 of
driving wheels through an input sensor 3 and memorizes it in a
memory 5. Further, the information of the rotational speeds of
wheels from a detection device 2 of the rotational speeds of wheels
is inputted to be memorized in the memory 5. The information of the
rotational speeds of wheels from a detection device 2 of the
rotational speeds of wheels may be pulses which are generated by
the speeds of wheels. In that case, the rotational speeds of wheels
can be calculated from the cycle of pulses inputted or the number
of pulses at a time interval. CPU 4 performs the detection program
of heterogeneous tires and the detection program of the decreased
tire pressures of the present invention stored in the memory 5. In
the present Embodiment, one memory 5 is described, but the program
may be divided to be memorized in ROM (read-only memory) and
calculation data may be divided to be memorized in RAM (random
access memory). Further, a display device 7 for alarming deflation
which displays the deflation alarm of the tire pressures being
judged and a control device 8 of driving a vehicle utilizing the
information of loading heterogeneous tires and the information of
the decreased tire pressures are connected thereto.
[0045] The driving axle of the vehicle is equipped with a
differential gear, and since driving torque differs at the left and
right driving wheels, torque sensors are provided at the respective
left and right driving wheels, but unless heterogeneous tires are
detected during the vehicle is cornering, the torque sensor may be
provided at one spot of a propeller shaft. A strain gauge of
measuring the strain of a driving axle can be used as the torque
sensor.
[0046] FIG. 2 is a flow chart showing an example of the detection
method of heterogeneous tires of the present invention. Referring
to FIG. 2, a method for detecting whether heterogeneous tires are
mounted on driving wheels is illustrated.
[0047] The rotational speeds of wheels mounted on a vehicle is
inputted from the detection device 2 of the rotational speeds of
wheels to determine the rotational speed ratio of the front and
rear wheels of right side wheels (Step S1) and the rotational speed
ratio of the front and rear wheels of left wheels (Step S2). Then,
the torque of driving wheels is inputted from the torque sensor 1
of driving wheels (Step S3). In fact, the rotational speeds of
wheels and the torque of driving wheels are simultaneously
inputted.
[0048] Steps S1 to S3 are repeated until data enough for being
capable of primarily approximating (regression straight lines are
determined) the relation between the torque of driving wheels and
the rotational speed ratios of the front and rear wheels of
respective left and right wheels are collected (Step S4). Hereat,
"capable of primarily approximating" means that the standard
deviation of a primary coefficient is adequately lessened in
comparison with the difference of inclinations of the detecting
heterogeneous tires described later (for example, the standard
deviation of a primary coefficient is less than 1/10 of the
threshold of the difference of inclinations). When the data of
required number of samples are collected, the regression straight
line of the relation between the torque of driving wheels and the
rotational speed ratio of the front and rear wheels of left side
wheels and the regression straight line of the relation between the
torque of driving wheels and the rotational speed ratio of the
front and rear wheels of right side wheels are determined, and
their respective inclinations are calculated (Step S5).
[0049] After comparing the inclination of the regression straight
line of left side wheels with the inclination of the regression
straight line of right side wheels, the difference is compared with
a predetermined value. Unless the difference of inclinations of the
regression straight lines of left and right wheels exceeds the
predetermined value, it is judged that the kinds of tires of the
respective left and right driving wheels are the same, and the
threshold for judging tire deflation is set as a threshold in the
case of the same kind of tires (Step S7). When the difference of
inclinations of the regression straight lines of left and right
wheels is the predetermined value or more, it is judged that the
kinds of tires at the respective left and right driving wheels are
different, and the threshold for judging tire deflation is set as a
threshold in the case of heterogeneous tires (Step S8).
[0050] The predetermined value c for judging the difference of
inclinations of the regression straight lines of left and right
wheels, or the predetermined value k for judging the ratio of
inclinations is set as; c=|a1-a2|/M k=1+(a1/a2-1)/N (provided that
a1>a2) or k=1+(a2/a1-1)/N (provided that a2>a1) [0051] from
|a1-a2| and a1/a2 (when a1>a2) or a2/a1 (when a2>a1), after
the fore-mentioned relations; Rotational .times. .times. speed
.times. .times. of .times. .times. left .times. .times. front
.times. .times. wheel / rotational .times. .times. speed .times.
.times. of .times. .times. left .times. .times. rear .times.
.times. wheel = a .times. .times. 1 .times. torque .times. .times.
to .times. .times. driving .times. .times. wheel + b1 ##EQU3##
Rotational .times. .times. speed .times. .times. of .times. .times.
right .times. .times. front .times. .times. wheel / rotational
.times. .times. speed .times. .times. of .times. .times. right
.times. .times. rear .times. .times. wheel = a .times. .times. 2
.times. torque .times. .times. to .times. .times. driving .times.
.times. wheel + b .times. .times. 2 , .times. ##EQU3.2## [0052] are
determined by changing the kind of tires (for example, tires for
summer or tires for winter) for every vehicle brand.
[0053] The denominator M or N of the fore-mentioned formulae for
determining c or k can be set as 2, for example, but the values of
M and N can be selected by vehicle brands and the kind of tires
(for example, tires for summer or tires for winter).
[0054] The threshold for judging tire deflation in case that the
kinds of tires on the respective left and right driving wheels are
different is preliminarily measured to be determined. It is
preferable that the threshold for judging tire deflation is set by
every combination of tires with different kinds of tires which can
be mounted on the vehicle. Since the threshold for judging tire
deflation is considered to be symmetric, the same threshold is used
even if different kinds of tires are reverse at left and right.
Namely, when the kinds of tires to be employed for a vehicle brand
are 3, there are 3 thresholds, and when the kinds of tires are 4,
there are 6 thresholds.
[0055] Further, it can be judged which of the left and right
driving wheels tends to slip, from the steepness of inclinations of
the regression straight lines of left and right wheels. In the
present Embodiment, since the rotational speed ratio of the
following wheels/the rotational speed of the driving wheels is
referred to as the rotational speed ratio of the front and rear
wheels, the inclination of the regression straight lines is
negative, and a tire having small inclination (the absolute value
of the inclination is large) tends to slip. Further, the kinds of
left and right tires can be judged by comparing the fore-mentioned
inclinations of the regression straight lines during running which
were primarily approximated, with the relation (the inclinations of
the straight lines primarily approximated) between the rotational
speed ratios of the front and rear wheels and the torque of driving
wheels which were preliminarily measured by every kind of tires
(for example, tires for summer or tires for winter).
[0056] Although not described in the flow chart of FIG. 2, it is
judged whether the tire is deflated by exceeding the deflation rate
which was set by the threshold, by comparing the threshold for
judging tire deflation which was set at Step S7 or Step S8, with
the threshold for judging tire deflation during running.
EXAMPLE
[0057] Then, an example in which the relation between the
fore-mentioned torque of driving wheels and the rotational speed
ratio of the front and rear wheels was compared at left and right
wheels in a real vehicle, for a case that the kinds of tires on the
respective left and right driving wheels are the same and a case
that the kinds of tires on the respective left and right driving
wheels are different.
[0058] An FR vehicle (Mercedes-Benz, E-class) was used for
experiment, and the experiment was carried out by running on a
general road under conditions of 2 persons boarding, normal tire
pressures and a tire size of 205/60R16, for a case that the
respective left and right driving wheels are the same kind and a
case that the respective left and right driving wheels are
different kinds.
[0059] FIG. 3 is a graph in which the rotational speeds of the
front wheels/the rotational speeds of the rear wheels of respective
left and right are plotted relative to driving torque when the same
kind of tires at the respective left and right driving wheels are
mounted.
[0060] FIG. 4 is a graph in which the rotational speeds of the
front wheels/the rotational speeds of the rear wheels of respective
left and right are plotted relative to driving torque when
heterogeneous tires at the respective left and right driving wheels
are mounted.
[0061] The inclination of driving torque--the rotational speed
ratio of front and rear wheels at the left side wheels was
-1.6.times.10.sup.-5 and the inclination of driving torque--the
rotational speed ratio of front and rear wheels at the right side
wheels was -1.7.times.10.sup.-5, in the case of the same kind of
tires of FIG. 3.
[0062] The inclination of driving torque--the rotational speed
ratio of front and rear wheels at the left side wheels was
-1.9.times.10.sup.-5 and the inclination of driving torque--the
rotational speed ratio of front and rear wheels at the right side
wheels was -2.3.times.10.sup.-5, in the case of the heterogeneous
tires of FIG. 4.
[0063] The difference of inclinations in the case of the same kind
of tires of FIG. 3 was 0.1.times.10.sup.-5 and the difference of
inclinations in the case of heterogeneous tires of FIG. 4 was
0.4.times.10.sup.-5; therefore the difference of inclinations of
the property of driving torque--the rotational speed ratios of
front and rear wheels at left and right is larger for the
heterogeneous tires. Then, when the difference of inclinations of
the property of driving torque--the rotational speed ratios of
front and rear wheels at left and right exceeds
0.2.times.10.sup.-5, it can be judged that heterogeneous tires are
mounted at the respective left and right driving wheels.
Alternatively, when the ratio of inclinations of the property of
driving torque--the rotational speed ratios of front and rear
wheels at left and right exceeds, for example, 1.1 times (or less
than 0.9 times), it can be judged that heterogeneous tires are
mounted on the respective left and right driving wheels.
[0064] The threshold of the difference of inclinations for judging
whether the fore-mentioned heterogeneous tires are mounted or not
is different by every type of vehicles. The properties of the
rotational speeds of front and rear wheels are preliminarily
measured by every type of vehicles and the threshold for judging
the mounted heterogeneous tires is set.
[0065] Further, since the inclination of the property of driving
torque--the rotational speed ratios of front and rear wheels at
right side is smaller under the condition of FIG. 4 (the absolute
value is larger), it can be judged that the wheel at right side
tends to slip.
[0066] In the case of the present Example, when the deflation rate
for judging the decreased tire pressure is 30% and the same kind of
tires are mounted at the respective left and right driving wheels,
the threshold for judging tire deflation by real measurement is 0.1
and when the heterogeneous tires are mounted at the respective left
and right driving wheels, the threshold for judging tire deflation
by real measurement is 0.13. These thresholds are preliminarily
memorized in the alarming device of the tire pressures and an
experiment of judging deflation was carried out by applying the
method shown in the flow chart of FIG. 2.
[0067] In the present Example, a value obtained by the following
formula is used as the judging value of the decreased tire
pressures;
((((W.sub.FL+W.sub.RR)/2)-((W.sub.FR+W.sub.RL)/2))/(W.sub.FL+W.sub.FR+W.s-
ub.RL+W.sub.RR)/4).times.100
[0068] Wherein W.sub.** represents the rotational speed of a wheel,
and ** represents the position of the wheel (FL: front left, FR:
front right, RL: rear left and RR: rear right).
[0069] Under the setting, when test running was carried out at
deflation of 10% for one wheel, thresholds in accordance with the
same kind of tires and the heterogeneous tires at the respective
left and right driving wheels are selected by the detection of
heterogeneous tires, and no alarm was given for either of a case of
the same kind of tires and a case of the heterogeneous tires.
[0070] Under the same setting, when test running was carried out at
deflation of 30% for one wheel, thresholds in accordance with the
same kind of tires and the heterogeneous tires at the respective
left and right driving wheels are selected by the detection of
heterogeneous tires, and alarm was given for either of a case of
the same kind of tires and a case of the heterogeneous tires.
[0071] Thus, when the heterogeneous tires are mounted at the
respective left and right driving wheels, an alarm that the
heterogeneous tires are mounted is given to a driver to promote
replacing tires. Referring to the fore-mentioned Example, when the
difference between the inclination of the property of driving
torque and the rotational speed ratios of front and rear wheels at
right side and the inclination of the property of driving torque
and the rotational speed ratios of front and rear wheels at left
side exceeds 0.2.times.10.sup.-5 in an FR vehicle (Mercedes-Benz,
E-class), it is judged that the heterogeneous tires are mounted at
the respective left and right driving wheels and it can be alarmed
to a driver that the heterogeneous tires are mounted.
[0072] Further, the detection of the decreased tire pressures can
be accurately carried out under the same deflation condition even
if the kind of tire is different, by setting the judgment
thresholds of deflation in accordance with the same or different
kind of tire at the respective left and right driving wheels.
Referring to the fore-mentioned Example, no deflation was judged
for either of a case that the same kind of tires was mounted at the
respective left and right driving wheels and a case that the
heterogeneous tires were mounted, in a state in which one wheel was
deflated by 10% in the FR vehicle (Mercedes-Benz, E-class).
Deflation could be judged for either of a case that the same kind
of tires was mounted at the respective left and right driving
wheels and a case that the heterogeneous tires were mounted, in a
state in which one wheel was deflated by 30%. Consequently, the
danger of tire deflation can be notified to a driver without fail
under the same deflation condition even if the kind of tire is
different, by setting the judgment thresholds of deflation in
accordance with the same or different tire classification at the
respective left and right driving wheels, utilizing the result of
the detection device of heterogeneous tires of the present
invention. The tire deflation cannot be judged in all types of
vehicles at the same deflation rate in case that the heterogeneous
tires are mounted, but according to the present invention, when the
heterogeneous tires were mounted and the tire pressures were not
reduced to a level for alarming, the alarm of tire deflation is not
falsely given at all.
[0073] In the present Example, an FR vehicle was used, however the
detection method of heterogeneous tires and the detection method of
the decreased tire pressures of the present invention are not
limited to the FR vehicle, but can be also similarly applied to an
FF vehicle, an RR vehicle, an MR vehicle and a 4 WD vehicle.
[0074] In the present invention, a case that the heterogeneous
tires are mounted was illustrated, but when the degree of abrasion
differs at the respective left and right driving wheels, it can be
detected that the degree of abrasion differs at the respective left
and right driving wheels, by comparing the inclination of the
property of driving torque and the rotational speed ratios of front
and rear wheels at left and right side of the present invention (a
case that the degree of abrasion differs is recognized as the
heterogeneous tires).
* * * * *